by Paul Gilster | Oct 15, 2007 | Astrobiology and SETI |
When Alexander Zaitsev presented his recent paper at the International Astronautical Congress in Hyderabad (India) recently, he spoke from the center of a widening controversy. The question is straightforward: Should we broadcast messages intentionally designed to be received by extraterrestrial civilizations, thereby notifying them of our existence? Zaitzev, chief scientist at the Russian Academy of Science’s Institute of Radio Engineering and Electronics, addressed the question by seeing a necessary relationship between SETI (the search for ETI) and METI (messaging to other civilizations).
Indeed, the Russian scientist, working at the Evpatoria Deep Space Center in the Ukraine, has the experience to discuss METI from a practical standpoint. Evpatoria has already transmitted a number of messages, the so-called ‘Cosmic Call’ signal (1999) being made up of various audio, video, image and data files submitted by people around the world. The later ‘Teen-Age Message,’ aimed at six Sun-like stars, was sent in 2001; another ‘Cosmic Call’ followed in 2003.
Zaitzev has in the interim emerged as a leading spokesman for direct messaging to extraterrestrial civilizations, an idea now hotly debated by a relatively small group of researchers concerned about its implications. I note the size of the debate pointedly — it is remarkable to me that an issue that has the potential of involving the entire human species in what could become a first contact scenario is known only to a limited number of professionals, within whose ranks there is by no means agreement.
Thus, having coffee with a neighbor not long ago, I brought up the SETI/METI debate, curious about his reaction. I asked whether he believed transmitting messages intentionally designed for contact was a sound idea. “What’s the problem?” he asked. “If anyone’s out there, the sooner we get to know them, the better.” When I urged caution, pointing out that we know nothing whatsoever about what an alien species might think or do, he smiled. Wasn’t I just bringing up tired science fiction scenarios like the movie Independence Day? And what about the ‘I Love Lucy’ factor?
The latter, of course, is that expanding sphere of electromagnetic radiation that seems to flag our presence in the form of old television and radio shows (Fred Mertz as Terra’s first ambassador to the stars — the mind boggles…). Whether or not such signals would actually be detectible is problematic, but Zaitsev turns to an even stronger source of signalling, planetary radars like Arecibo, Goldstone and Evpatoria itself, whose active search for near-Earth asteroids would represent a more likely chance for reception.
When Zaitsev analyzed radar observations of asteroids and comets at the three radar sites, he found that none of these transmissions crosses the habitable zone of a star. That would imply that a civilization like our own, restricted to its own planet, would be unlikely to pick them up. In any case, a civilization bound to its own planet presents no threat to Earth in the first place. Whereas Kardashev Type II or III civilizations, with far greater energy resources at their disposal and presumably at home in interstellar space, would be more likely to receive them.
In his paper, Zaitsev puts the matter this way:
Accidental detection by such civilizations of signals from the planetary and asteroid radars of some other civilization is extremely unlikely. If we are afraid of powerful and aggressive civilizations of Type II and Type III, which live “practically everywhere”, it is necessary to forbid numerous pointless transmissions of asteroid and planetary radars as their radiation gradually illuminates greater areas that promotes its detection by ‘star aggressors and interventionists.’
In other words, if we’re serious about trying to keep our existence unknown, we had better stop using our planetary radars in the first place, which would mean giving up our protection against catastrophic strikes on Earth by comets or asteroids. It’s ironic that we’re discussing closing Arecibo’s planetary radar as we ponder such matters, but in any case, Zaitsev goes on to argue that there is less danger from interstellar messages like Evpatoria’s, targeted at specific stars, than the radar transmissions we have been making for some time in our own defense.
Zaitsev sees a close connection between SETI and METI in that both require an identical selection from the same target star lists, both involve consideration of optimum frequencies and likelihoods of success, so that the question of where to search and where to send are equivalent. He calls for the further use of Arecibo, Goldstone and Evpatoria in sending future interstellar messages, and notes that SETI itself may be dangerous. What if an uncontrolled SETI search ended up with fanatics in control of weapons derived from knowledge received from a high-level civilization?
As an onlooker in this debate for some time now, I keep running into a crucial problem. Again, it is the size of the participating audience. David Brin has been an advocate of the idea that we need wider involvement from other discipilines in deciding how to handle the METI question, and I have to agree with that assessment. It would be interesting to learn of any first-contact situation on Earth involving a technologically superior civilization and a less developed one where the latter did not suffer.
I admit to having little patience with sociology, but it would certainly be helpful to have a historian’s take on all this, and for that matter, people in the arts. We have a model for this kind of gathering. It is the 1983 Los Alamos meeting called the Conference on Interstellar Migration and the Human Experience. There, biologist met social scientist, historian met physicist, in an attempt to put our past human experience into perspective as we look forward to a future beyond the Solar System.
Why relate possible alien contact to scenarios that are expressly human? Because these are all we have to work with, and therefore must form the basis of our investigation. Which raises another troubling question. Human nature has shown its colors for good and ill throughout recorded history, a mixed record of dazzling achievements and horrific barbarism, depending on where you look. Would aliens be better than us, or worse? Or would they be much like us in having a mixture of motivations of the sort that in our own history has often led to misunderstandings, brutality and war?
At this point these can only be speculations. But how helpful it would be to see a meeting like the Conference on Interstellar Migration convened to address these matters from as wide a range of perspectives as possible. The interest for such a gathering seems to be growing. I would hope it could also raise the consciousness of the general public to an issue that, as we continue our technological advance, may well play a role in our long-term future. SETI/METI is a good story, but it’s not science fiction any more. And we need to establish an informed consensus before we send more messages.
Dr. Zaitsev’s paper “Sending and Searching for Interstellar Messages” is now available online. For more on the Los Alamos conference, see Ben R. Finney and Eric M. Jones, Interstellar Migration and the Human Experience (Berkeley: University of California Press, 1985).
by Paul Gilster | Oct 13, 2007 | Exotic Physics |
Fifty years ago, our understanding of space included only some of the properties we now find most intriguing from the standpoint not only of physics but also of potential propulsion. Dark energy was not suspected then, while Fritz Zwicky’s inference of dark matter (1933) wouldn’t really inspire a wave of investigations until the 1970’s. The presence of the quantum fluctuations that would later be dubbed Zero Point Energy had only recently been examined. For that matter, the cosmic microwave background was still almost a decade from discovery.
Knowing that such properties exist out there in the cosmos offers the potential of future technologies that might be able to make use of them. But clearly, we are a long way from understanding whether or if such phenomena could eventually be harnessed. Just how far becomes apparent every time we get new dark energy news, as we recently did from the University of Toronto, where astronomers studying supernovae in nearby galaxies found when comparing them to far more distant ones that the older supernovae were brighter.
That adds yet another problem to the dark energy picture, because the assumption of uniform brightness in these exploding stars has been helpful in understanding the universe’s accelerated expansion. Correcting for varying brightness could be a thorny problem, says Andrew Howell, lead author of the study:
“You can think of supernovae as light bulbs. We found that the early universe supernovae had a higher wattage, but as long as we can figure out the wattage, we should be able to correct for that. Learning more about dark energy is going to take very precise corrections though and we aren’t sure how well we can do that yet.”
We’d also like to know whether dark energy varies over cosmic time. After all, the term in play is ‘cosmological constant,’ but just how constant is it? Trying to figure out how dark energy behaved in the early universe may require studying radio emissions from neutral hydrogen, redshifted by the expansion of the universe. Stuart B. Wyithe (University of Melbourne) and Avi Loeb (Harvard-Smithsonian Center for Astrophysics) want to study such emissions, believing that although most hydrogen from that era was ionized, surviving neutral clumps may still be detectable.
Does neutral hydrogen show the same kind of distribution patterns as galaxies, caused by early fluctuations in energy density and pressure? Studying its distribution should provide clues as to dark energy’s role in the first few billion years. Wyithe and Loeb believe instruments now being built such as the Murchison Wide-field Array could detect the faint signals from the neutral hydrogen that could tell the tale.
Given the revolution in our understanding of the universe’s expansion, we can assume that the investigation of dark energy will continue to be a primary thrust of modern physics. Which reminds me that a focus of the Breakthrough Propulsion Physics program at NASA was to introduce a targeted perspective — applications to spaceflight — within which recent physics advances could be studied, in hopes of generating new lines of inquiry. The hope: Even if propulsion breakthroughs do not emerge, their study may add to the pool of scientific knowledge.
That’s a worthy goal, and we will need all the perspectives we can find to approach problems as thorny as dark energy. The Toronto paper is Howell et al., “Predicted and Observed Evolution in the Mean Properties of Type Ia Supernovae with Redshift,” Astrophysical Journal 667, pp. L37-L40 (abstract). You can find Loeb and Wyithe’s paper “Fluctuations in 21cm Emission After Reionization” here. The mind boggles at how vast the future bibliography of dark energy studies will become.
by Paul Gilster | Oct 12, 2007 | Astrobiology and SETI |
The Allen Telescope Array, devoted both to SETI and astronomical observations, has begun operations. With 42 radio dishes now active, the array ultimately will be used to scan several billion stars in the Milky Way looking for the signals of an extraterrestrial civilization. That’s a staggeringly broad survey, and one that will be followed up by detailed examinations of a million star sample. The ATA is known as Paul Allen’s project, but he’s joined in philanthropy by the SETI Institute and UC Berkeley, among others.
Says Seth Shostak (SETI Institute):
“For SETI, the ATA’s technical capabilities exponentially increase our ability to search for intelligent signals, and may lead to the discovery of thinking beings elsewhere in the universe. It is the first major telescope in the world built specifically for undertaking a search for extraterrestrial intelligence.”
It’s always interesting to track how the press handles such stories, and this Seattle Times‘ article plays it straight, with a description of the installation’s 42 radio dishes northeast of San Francisco (at Hat Creek in the Cascade Mountains north of Lassen Peak) and their potential use for the study of astronomical phenomena — pulsars, supernovae, black holes, gravity waves — as well as the ongoing SETI work. Allen, who also backed the winning entry in the X-prize competition, recalls reading Heinlein’s Rocket Ship Galileo as the defining moment in creating his youthful interest in space.
Image: The Allen Telescope Array now begins observations. Hat Creek will eventually see 350 such dishes mining the sky for radio astronomy and SETI investigations. Credit: ATA/SETI Institute.
With the ATA now engaged in active research, we can ponder the differences between it and other observing programs. Time on Arecibo’s huge dish was necessarily limited, with the SETI Institute’s Project Phoenix managing to use the instrument for just three weeks each spring and fall. That added up to a total of 100 observing days between September of 1998 and March of 2004. The Allen Telescope Array offers 24-hour a day access seven days a week.
Moreover, the frequencies available to the ATA — between 1000 and 10,000 MHz — cover five times the range of Project Phoenix. With 350 individual dishes planned for the site, the ATA should be able to examine multiple stars simultaneously, another step up from Arecibo. Thus Project Phoenix’s observations (covering roughly 800 stars) can be upped to the huge numbers Allen’s team envisions, a major step forward for SETI work.
But will the new array produce better results than Project Phoenix itself, which found no sign of intelligent extraterrestrials? As always, that’s the biggest SETI question, and those of us who doubt that advanced civilizations are numerous in the galaxy won’t be surprised if a detection takes a long time, if and when it comes. But the ATA model, using mass-produced 6.1-meter radio dishes and commercial telecommunications technologies, seems the way to go, particularly since it’s backed by philanthropic funding.
$50 million is buying a lot of observing power (see this news release for funding details). We can hope for a breakthrough reception, but even if it doesn’t come, we’re gaining an instrument whose multi-tasking capabilities allow radio astronomy to be conducted on a daily basis even as the search continues. In those terms, this is a gamble well worth taking, and one with significant payout no matter what the SETI outcome.
by Paul Gilster | Oct 11, 2007 | Outer Solar System |
Xanadu seems to be a misty, drizzly place. So say new images showing a persistent light rain of methane over the western foothills of this, the major continent of Titan. Titan’s day is sixteen Earth days long, so if we say the drizzle or mist dissipates after about 10:30 AM local time, we’re saying that it lasts until three Earth days after sunrise. As much as the Sun ever rises on this frigid, cloud-bound world.
The work, conducted using data from the Keck Observatory (Hawaii) and Very Large Telescope (Chile), was presented today at the Division for Planetary Sciences meeting in Orlando (FL). The findings mark the first direct observation of methane rain, although precipitation has been presumed to occur for some time now. Features near Titan’s poles have been interpreted as lakes of liquid hydrocarbons, presumably replenished by just such precipitation.
Image: VLT and Keck near-infrared images of Titan’s surface and lower
troposphere can be subtracted to reveal widespread cirrus-like clouds of frozen methane (lower images) and a large patch of liquid methane (dark area within box) interpreted as clouds and morning drizzle above the huge continent of Xanadu (outline). At left is a chart of Titan’s aerosol haze versus altitude, indicating higher density haze over portions of the south pole and the heights of frozen and liquid methane clouds. Credit: Mate Adamkovics/UC Berkeley, W. M. Keck Observatories, ESO.
The researchers, Máté Ádámkovics and Imke de Pater (UC Berkeley), see the widespread drizzle as a possibly dominant mechanism for returning methane to the surface, thus closing the methane cycle in a way similar to how the water cycle operates on Earth. The first images of actual clouds on the moon were the work of de Pater’s group, finding frozen methane clouds at an elevation of some 30 kilometers over Titan’s south pole. That work was done in 2001, since which time much data on the clouds has accumulated. Liquid methane clouds seem to occur below 20 kilometers.
In any case, getting a read on precipitation is hard work. Says Ádámkovics:
“The stratiform clouds we see are like cirrus clouds on Earth. One difference is that the methane droplets are predicted to be at least millimeter-sized on Titan, as opposed to micron-sized in terrestrial clouds – a thousand times smaller. Since the clouds have about the same moisture content as Earth’s clouds, this means the droplets on Titan are much more spread out and have a lower density in the atmosphere, which makes the clouds ‘subvisible’ and thus hard to detect.”
You need to do this kind of work at infrared wavelengths because Titan’s haze then becomes relatively transparent rather than presenting the impenetrable layers of smog seen in optical wavelengths. Using different infrared wavelengths, the researchers could probe the atmosphere at a range of altitudes, creating a methane absorption profile that allowed analysis of the clouds and their attendant drizzle. Tricky work, this, its methodology fully explained in today’s issue of Science Express, where the paper is Ádámkovics et al., “Widespread Morning Drizzle on Titan” (abstract).
Related: New Cassini views of Titan’s lakes and seas, with lakes also discovered around Titan’s south pole, have just become available.
by Paul Gilster | Oct 10, 2007 | Outer Solar System |
Ever since the launch of New Horizons in January of 2006 (can it really be that long?), the prospects of doing good science as the spacecraft whipped through the Jupiter system have tantalized and intrigued us. Eight spacecraft have now visited Jupiter, but New Horizons found things no previous mission had witnessed, including the evolution of a volcanic plume, lightning near the planet’s poles, a tighter look at the Jovian rings and a trip down the unexplored length of the planet’s magnetic tail.
In addition to providing the gravity boost that will get New Horizons to Pluto faster, the Jupiter encounter was a valuable chance to shake out the spacecraft’s instruments in preparation for the later encounter. And to hear principal investigator Alan Stern tell it, nothing could have gone better:
“The Jupiter encounter was successful beyond our wildest dreams. Not only did it prove out our spacecraft and put it on course to reach Pluto in 2015, it was a chance for us to take sophisticated instruments to places in the Jovian system where other spacecraft couldn’t go, and to return important data that adds tremendously to our understanding of the solar system’s largest planet and its moons, rings and atmosphere.”
All of which makes me wish I could have attended the Division for Planetary Sciences meeting in Orlando this week, where these results were presented (they’ll also appear in a special section of Science). The Io work was particularly fruitful, spotting eleven volcanic plumes, one of them rising 290 kilometers high above the volcano Tvashtar. In addition to the Tvashtar plume, which could be studied condensing and falling back to Io’s surface, New Horizons picked up the infrared signature of 36 volcanoes and measured lava temperatures.
Image: The Tvashtar plume, reaching 290 km above the surface, along with other plumes and hot spots. Credit: Alan Stern.
Io’s tortured surface was expected to be highly changeable, and indeed it is, with twenty geological changes since the Galileo mission’s last look in 2001. Interestingly, glowing gas clouds appear above dozens of the volcanoes when Io passes into Jupiter’s shadow, evidently resupplying the tiny world’s atmosphere. Here’s Kurt Retherford (SwRI) on the matter:
“When Io goes into solar eclipse, and during the night, its surface temperature drops significantly, causing diminished sublimation of surface material into the atmosphere. The atmosphere at that point collapses down so that all that is left supplying the atmosphere are the volcanoes.”
Moreover, evidence of tons of material from Io’s volcanoes moving down Jupiter’s magnetic tail in slow-moving blobs was found by New Horizons’ particle detectors. For more, including new looks at Jupiter’s meteorology and slides on all the above from the presentation at DPS, check this news release at the New Horizons site. I’ll be posting the complete references to the Science papers as soon as they become available.
